However, I do not wish to interpret the mustache, but to speculate about its sources. The analogy most often drawn is to Vincent Price, and words like creepy, spectral, and cheesy have been used with abandon. However, no one has yet been able to provide a convincing reason why Bob Dylan, the greatest songwriter of our times, should wish to emulate a horror-movie icon. The "Price theory" must, despite its popularity (examples here and here), be judged a failure.
I want instead to propose a more logical forebear for the mustache, and one with textual links to Dylan's own oeuvre. In his recently released memoir, Chronicles, Volume One (Scribner), Dylan remembers his meeting with folk legend Cisco Houston. One of his sentences provides the key to the riddle:
Cisco, handsome and dashing with a pencil thin mustache, looked like a riverboat gambler, like Errol Flynn. (p. 63)
Is it not clear that Dylan's mustache is inspired by Cisco Houston's mustache? It is true that Dylan's music at the present time does not resemble Houston's, but this is unquestionably due to the "anxiety of influence" exposited so unforgettably by Harold Bloom.
To further clinch the identification, many will remember that Cisco Houston is actually mentioned in Dylan's first song, "Song to Woody":
Here's to Cisco an' Sonny an' Leadbelly too,
An' to all the good people that traveled with you.
Here's to the hearts and the hands of the men
That come with the dust and are gone with the wind.
That eulogistic tone -- and it surely encompasses the facial hair -- is unmistakable. Dylan inherited not only the role of Woody Guthrie's sidekick, but also the sidekick's mustache.
But still, I will leave it you to decide: Bob Dylan's mustache:
Vincent Price or Cisco Houston?
UPDATE: Ann Althouse discusses Dylan and facial hair here.